One manner in which glass is conventionally bent and tempered is with press benders having shaped surfaces between which heated glass is clamped to shape it prior to being air cooled by a quench unit to provide tempering. U.S. Pat. Nos. 3,454,389; 3,476,542; 3,488,178; 3,600,150 and 3,951,634 disclose press bending and tempering apparatus for sheet glass.
Sheet glass is also bent and tempered by heating of planar glass sheets while supported on bending molds including movable sections. Prior to softening of the glass during heating, the sections of the mold are oriented to accommodate for the glass sheet planarity. Upon softening of the glass sheet as it is heated, the mold sections move relative to each other under the force of gravity acting on the glass sheet and on the mold sections in order to provide bending of the glass sheet prior to rapid cooling thereof which provides its tempering. Thin glass, i.e. on the order of 1/8", cannot be bent by this apparatus since it does not have sufficient weight to provide the impetus for pivoting the mold sections under the force of gravity and the thin glass would overbend before becoming hot enough to temper. U.S. Pat. Nos. 3,269,822; 3,278,287; 3,307,930 and 3,365,285 disclose this type of bending and tempering apparatus.
Heating of glass sheets prior to bending and tempering thereof has also been performed on fluid support beds as the glass is conveyed through a furnace. Normally the support bed is inclined slightly with respect to the horizontal so that gravity engages an edge of the glass with a movable frame that provides the impetus for glass movement along the bed. The fluid support from below the glass is sufficient to avoid contact between the bed and the lower surface of the glass during conveyance of the glass as it is heated and softened, but is otherwise insufficient to provide controlled vertical displacement of the glass, as the shape of the apertures in the support bed and the normal operating pressure typically provide only nominal support of the glass above the support bed of about one-eighth inch. This lack of contact prevents marring and scratching of the soft surfaces of the glass as the glass reaches its deformation temperature. However, there normally is mechanical contact with the glass during the bending after the heating in preparation for the cooling quench that tempers the glass in its bent condition. U.S. Pat. Nos. 3,497,340; 3,607,187; and 3,607,200 disclose glass bending and tempering apparatus of this type with a fluid support bed.
Vacuum forming of heated glass sheets is disclosed by U.S. Pat. No. 3,778,244 wherein sheet glass is first heated during conveyance along a roller hearth conveyor. After heating, a holder with a curved downwardly facing surface has a vacuum applied thereto about the surface to shape the glass. After shaping against the curved surface of the holder, the vacuum is terminated to drop the glass onto a mold for conveyance to a waiting operator who removes the glass from the mold. Further vacuum forming of the glass to a curved surface of the mold is also disclosed.
Other bending and tempering apparatus for sheet glass is disclosed by U.S. Pat. Nos. 2,223,124; 2,348,887; 2,646,647; and 2,085,520.